A new organ has been discovered hiding in plain sight inside the human body.

The organ is known as the mesentery and it was previously thought to be just a few fragmented structures in the digestive system.

But now scientists at the University of Limerick have realised it is in fact one, continuous organ.

Although its function is still unclear, the discovery opens up “a whole new area of science,” according to J Calvin Coffey, a researcher at the UL who first discovered it.

Professor J Calvin Coffey

"When we approach it like every other organ… we can categorise abdominal disease in terms of this organ," he said.

“Now we have established anatomy and the structure. The next step is the function. If you understand the function you can identify abnormal function, and then you have disease.

“Put them all together and you have the field of mesenteric science.”

Professor Coffey's research has been published in The Lancet medical journal.

A digital representation of the small and large intestines and associated mesentery J Calvin Coffey, D Peter O’Leary, Henry Vandyke Carter

Following its reclassification, medical students are now being taught that the mesentery is a distinct organ.

Gray’s Anatomy, the world’s most famous medical textbook, has been updated to include the new definition.

According to the UK Independent medical students and researchers can now investigate what role the mesentery might play in abdominal diseases, which it is hoped could ultimately lead to new treatments.

The organ is a double fold of peritoneum - the lining of the abdominal cavity - that holds our intestine to the wall of our abdomen.

The organ was first described by the Italian polymath Leanardo da Vinci in 1508, but it has been ignored throughout the centuries, until now.

Although there are generally considered to be five organs in the human body, there are in fact now 79, including the mesentery.

The heart, brain, liver, lungs and kidneys are the vital organs, but there are another 74 that play a role in keeping us healthy.